(a) Technical Field of the Invention
The present invention generally relates to bicycle handbrakes, and more specifically to a U-type bicycle handbrake assembly structure.
(b) Description of the Prior Art
The bicycle handbrake is the key to the rider's safety. To brake the bicycle quickly, the brake arms of the handbrake has to be correctly hinged to the bicycle frame. The brake pads at the bottom of the brake arms should be disposed at either side of the wheel and should have an equal distance to the wheel rim, so that the brake pads could by pulled horizontally and symmetrically into engagement with wheel rim to slow or stop the bicycle.
Conventionally a U-type handbrake has its two brake arms hinged to the bicycle frame respectively and crossed with each other in an “X” configuration. Then a brake wire is connected to the upper ends of both brake arms so that, when the brake wire is pulled, the two brake pads on the other ends of the brake arms clips the wheel rim simultaneously.
FIG. 6 is an explosion perspective view of a brake arm of a conventional U-type handbrake. As illustrated, the brake arm 4 has a brake pad 41 at the bottom. During assembly, the brake arm 4 is pin-joined to the bicycle frame by screwing a bolt 43 through the brake arm 4 into a bolt hole 421 of the fitting tube 42 on the bicycle frame. Between the bolt 43 and the brake arm 4, there is a spring protection seat 45 containing a return spring 44 inside which is sleeved over by an adjusting seat 46. An end of the return spring 44 passes through the spring protection seat 45 and into a hole 40 on the brake arm 4. The other end of the return spring 44 is positioned against the inner side of the adjusting seat 46. To adjust the position of the brake arm 4, the bolt 43 is screwed loosed first. Then a tool is used to clamp the surface 461 and rotate the adjusting seat 44 so that the spring 44 could move the brake arm 4. However, to position a brake arm in its final place, a user constantly has to use one tool to tighten and loose the bolt 43 for many times. In the mean time, the user has to use another tool to clamp the surface 461 of the adjusting seat 46, and frequently the user has to grip a handbrake operating device on the handlebar to test if the brake arms are in the appropriate positions. More over, as the return spring 44 tends to resist the adjustment, if the bolt 43 is screwed in time to fix the adjusting seat 46, the return spring 44 would void all the adjustment arranged so far.